Nilsson appeared in three games for the Blues last season, posting a 2.76 goals-against average and a .909 save-percentage. He was originally acquired to give the Blues some depth between the pipes while Jake Allen and Brian Elliott battled injuries during the 2015-16 season.
On Friday, the Blues signed Allen to a four-year contract extension through the 2020-21 season and signed free agent goalie Carter Hutton to a two-year deal.